除以苯為原料和C4烴為原料兩條路線外，用萘或二甲苯鄰苯二甲酸酐時也副產(chǎn)順酐，每噸鄰苯二甲酸酐大約可回收50kg的純順酐。下面
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In addition to the two routes of using benzene as the raw material and C4 hydrocarbon as the raw material, the production of phthalic anhydride from naphthalene or xylene also produces maleic anhydride as a byproduct. Approximately 50kg of pure maleic anhydride can be recovered per ton of phthalic anhydride produced. Let's talk more about maleic anhydride manufacturers.
苯氧化法
Benzene oxidation method
苯氧化為順酐是在催化劑存在下進(jìn)行的。常用催化劑的活性組分均為釩的氧化物（見金屬氧化物催化劑），為抑制苯被完全氧化，常加入鉬、磷、鈦、鎢、銀及堿金屬等元素的氧化物為添加劑，并采用低比表面的惰性物質(zhì)為催化劑載體，如α-氧化鋁、剛玉等。
The oxidation of benzene to maleic anhydride occurs in the presence of a catalyst. The active components of commonly used catalysts are vanadium oxides (see metal oxide catalysts). To suppress the complete oxidation of benzene, oxides of elements such as molybdenum, phosphorus, titanium, tungsten, silver, and alkali metals are often added as additives, and inert substances with low specific surface area are used as catalyst carriers, such as α- Aluminum oxide, corundum, etc.
反應(yīng)在常壓下進(jìn)行，溫度350～400℃。工藝過程由苯的氧化，順酐的分離和提純兩大部分組成（見圖）。苯蒸氣和空氣能形成爆炸混合物，所以進(jìn)入反應(yīng)器的混合氣中，苯的濃度應(yīng)在爆炸極限之外，一般為1％～1.4％(摩爾)。
The reaction takes place under atmospheric pressure at a temperature of 350-400 ℃. The process consists of two main components: oxidation of benzene, separation and purification of maleic anhydride (see figure). Benzene vapor and air can form explosive mixtures, so the concentration of benzene in the mixed gas entering the reactor should be outside the explosion limit, usually 1% to 1.4% (mol).
苯氧化為強(qiáng)放熱反應(yīng)，工業(yè)上常采用列管式固定床反應(yīng)器，有很大的傳熱面，管外為冷卻系統(tǒng)，反應(yīng)熱可用于產(chǎn)生高壓蒸汽。離開反應(yīng)器的氣體中含順酐約1％（摩爾），用冷卻的辦法可將其中所含一半左右的順酐冷凝為液體，其余部分則用吸收法回收。
Benzene oxidation is a strong exothermic reaction. Tubular fixed bed reactors are often used in industry. They have a large heat transfer surface. Outside the tubes, there is a cooling system. The reaction heat can be used to generate high-pressure steam. The gas leaving the reactor contains about 1% (mole) of maleic anhydride. About half of the maleic anhydride can be condensed into a liquid by cooling, and the rest can be recovered by absorption.
吸收劑用水或惰性有機(jī)溶劑，大多數(shù)工廠采用的是水。所得到的吸收液是順丁烯二酸的水溶液，濃度35％～40％(質(zhì)量)，需用共沸溶劑（例如二甲苯、苯甲醚）進(jìn)行脫水，把酸重新轉(zhuǎn)化成酸酐。脫水也可在膜式蒸發(fā)器中進(jìn)行。粗酐經(jīng)減壓精餾可得成品。以苯計(jì)算，整個過程的順酐收率為92％～96％（質(zhì)量）。
Absorbent water or inert organic solvents, most factories use water. The obtained absorption solution is an aqueous solution of maleic acid, with a concentration of 35-40% (mass). It needs to be dehydrated using an azeotropic solvent (such as xylene, anisole) to convert the acid back into anhydride. Dehydration can also be carried out in membrane evaporators. Crude anhydride can be obtained by vacuum distillation to obtain finished products. Calculated with benzene, the yield of maleic anhydride in the entire process is 92% to 96% by mass.
C4烴氧化法
C4 hydrocarbon oxidation method
正丁烷與丁烯均含有與順酐相同的碳原子數(shù)，是順酐的理想原料。由于正丁烷較其他原料低廉，用正丁烷更為有利。其流程與苯氧化法基本相同，催化劑為釩-磷-氧體系，添加劑有鐵、鉛、鋅、銅、銻等元素的氧化物。
Both n-butane and butene contain the same number of carbon atoms as maleic anhydride, making them ideal raw materials for producing maleic anhydride. Due to the lower price of n-butane compared to other raw materials, using n-butane is more advantageous. The process is basically the same as the benzene oxidation method, with a vanadium phosphorus oxygen system as the catalyst and oxides of elements such as iron, lead, zinc, copper, and antimony as additives.
可用固定床反應(yīng)器或用流化床反應(yīng)器，反應(yīng)溫度約400℃。正丁烷-空氣混合物中正丁烷濃度為1.0％～1.6％(摩爾)。整個過程的順酐收率按正丁烷計(jì)約為50％。
A fixed bed reactor or a fluidized bed reactor can be used, with a reaction temperature of about 400 ℃. The concentration of n-butane in the n-butane air mixture ranges from 1.0% to 1.6% (mol). The yield of maleic anhydride in the entire process is approximately 50% based on n-butane.
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